HITCHCOCK AND CHASE— NORTH AMERICAN GRASSES. 47 



In this revision "involucre " and " bur " are used as having no 

 morphological significance, involucre meaning a covering or envelope 

 only and bur a spiny fruit. The "body of the bur" is the cup- 

 shaped or globose part formed by the coalesced part of the branch- 

 lets, from which the free ends extend. The " lobes " are the free 

 ends of the innermost ring of branchlets which form the body. In 

 some species they differ in appearance from the outer spines. 



The inflorescence is, morphologically, a contracted panicle with 

 short fascicled branches, these disarticulating from the main axis, 

 all but a few of them being sterile. For convenience the inflorescence 

 is here termed " spike," because it appears to be a spike, though 

 morphologically it is a panicle. 



HISTORY OF THE GENUS. 



The sandburs were known to pre-Linnaean botanists from garden 

 specimens only, or from a very few collections from the New World. 

 Comparatively few references to them are found in pre-Linnaean 

 botanical works. A common weed of the Mediterranean region, 

 Echinaria capitata, with spikelets of spiny-lobed florets, crowded in 

 a globose head, was commonly grouped with the sandburs by the 

 early authors, and was included in Cenchrus by Linnaeus when he 

 established that genus. The following phrase names have been 

 identified as applying to species of Cenchrus : 



Gramen Americanurn spica echinata majoribus locustis. Scholz, Hort. Vratis. 

 Cat. Bot. 258. 1587. This phrase uame is cited by Plukenet (Phytographie 2: 

 177, pi. 92. f. 3. 1696), whose figure is a fairly good illustration of Cenchrus 

 echinatus, and by others. Scholz's work has not been seen. 



Amongeaba. Piso, Med. Bras. 120. 1648. The colored plate is a crude illus- 

 tration of Cenchrus echinatus or C. viridis. It is more like the latter. 



Gramen tribuloides spicatum maximum Virginianum. Pluk. Phytog. 2: 177. 

 1696. If the specimen or seed was sent from Virginia, as indicated by the 

 name, it is doubtless C. tribuloides. 



Gramen echinatum maximum spica rubra vel alba. Sloane, Cat. Plant. Jam. 

 SO. 1696. Sloane's specimen so named, from Jamaica, preserved in the British 

 Museum of Natural History, 1 is C. echinatus. 



Gramen maritimum echinatum procumbens culmo longiori & spicis strigo- 

 sioribus. In Insula parva arenosa Gun cayos dicta non procul ab urbe Port- 

 Royal collegi. Sloane, Cat. Plant. Jam. 30. 1696; Hist. Jam. 1: 108. pi. 

 65. f. 1. 1707. The plate represents a plant of C. pauciflorus very like Hitch- 

 cock's no. 9637 from Black River, Jamaica. 



Gramen echinatum spicatum locustis crassioribus tribuloidibus Virginianum. 

 E seminibus e Virginia transmissis. Moris. PI. Hist. 3: 195. pi. 5. 1699. 

 The figure represents C. tribuloides. 



Gramen locustis tumidioribus, echinatis. Scheuch. Agrost. Hist. 77. 1719. 

 Described from a specimen in the Royal Garden at Montpellier. The descrip- 

 tion of the slender, horrid spines spreading on all sides identifies this as 

 some species of Cenchrus. 



*See Hitchcock, Contr. U. S. Nat. Herb. 12: 131. 1908. 



